Field of the Invention
The present invention relates to an image forming apparatus and a method for controlling the image forming apparatus.
Description of the Related Art
Hard disk drives (HDDs) are nonvolatile storage devices. HDDs have advantages including a low price per bit, high capacity, and an unlimited number of rewrite cycles, but have disadvantages including intermediate-speed processing performance and vulnerability to vibrations because of their mechanical structures. In recent years, solid-state drives (SSDs) using flash memories have been rapidly spreading. SSDs are storage devices including semiconductor elements and thus are resistant to vibrations. SSDs also have an advantage of processing speed twice or more as high as that of HDDs. SSDs have however fewer rewrite cycles per block unit due to miniaturization. Multi-level cell (MLC) SSDs have a number of rewrite cycles as extremely small as approximately 1000 to 3000 cycles. Although the high-speed performance of SSDs is advantageous, the SSDs' short service life in terms of rewrite cycles is a fatal disadvantage to cache systems, database apparatuses, and printing apparatuses in which the rewriting frequency is high.
Methods for extending the service life of a storage device, such as an SSD, using flash memory have been known. Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2013-513186 discusses a data cache system including a hybrid configuration of an SSD and an HDD. According to Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2013-513186, a data write cache is temporarily stored in the HDD, and the cached data is transferred to the SSD according to a transfer policy in consideration of the service life of the SSD.
Japanese Patent Application Laid-Open No. 2012-14632 discusses a service life extension method in which a data table of high update frequency is generated on a long service life storage device (HDD) and a table data of low update frequency is generated on a flash memory based on the update frequency of data, based on the update frequency of write data, in a database apparatus.
However, the methods discussed in Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2013-513186 and Japanese Patent Application Laid-Open No. 2012-14632 are difficult to apply to high-end printing apparatuses which need to realize both high resolution and high-speed printing. The method discussed in Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2013-513186 is not able to satisfy an output page per minute (PPM) specification of the printing apparatuses because of the processing performance of the HDD. The method discussed in Japanese Patent Application Laid-Open No. 2012-14632 is difficult to apply to a printing apparatus, from the viewpoint of statistic values such as update frequency.